Abdominal wound dressing

ABSTRACT

An abdominal wound dressing and methods of use are described that enable the application of negative pressure to the wound site in a healing manner while also limiting the formation of adhesions that would prevent the removal of the dressing. The dressing comprises a layer of porous foam material enclosed by sheets of elastomeric material punctuated by a number of appropriately placed holes. Multiple layers of porous foam may also be used. A suction tube connector is provided on an upper surface of a layer of foam for connection to a negative pressure source. At least one layer of foam is enclosed in elastomeric material and is placed in direct contact with the tissue within the open wound. Fluids are drawn by negative pressure through the holes positioned in the elastomeric envelope and through the foam.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/113,914, filed May 23, 2011, which is a divisional of U.S. patentapplication Ser. No. 12/127,668, filed May 27, 2008, which is acontinuation of U.S. patent application Ser. No. 10/275,671, filed Jun.10, 2003, now U.S. Pat. No. 7,381,859, which was the National Stage ofInternational Application No. PCT/GB01/02035, filed May 9, 2001, whichclaimed the benefit of Great Britain Application No. 0011202.9, filedMay 9, 2000. All of these applications are hereby incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates generally to methods and devices used for healingwounds caused by injury or surgery, and more specifically to methods anddevices for facilitating the healing of open wounds such as abdominalwounds that benefit from temporary closure and later reopening beforefinal closure.

2. Description of Related Art

Significant advances have been made in preventing postoperativeinfections. Still, post operative treatment of patients receiving manytypes of invasive surgeries, especially those involving the abdominalcavity, is enhanced by the ability to re-enter the cavity in order toaddress peritonitis and other infections that often inhibit the finalhealing of the wound and the internal organs. While the optimum outcomeis no post-operative infections or other complications whatsoever, suchcomplications occur frequently. Their occurrence has lead to the nowcommon practice of establishing a temporary wound closure and, later,re-entering the wound for the purposes of cleansing the abdominalcavity, and for treating such complications, which must be treatedbefore final, or definitive, closure.

The background description in U.S. Pat. No. 5,437,683 issued to Neumannet al., entitled Surgical Closure, the disclosure of which isincorporated herein by reference, reviews various complicationsassociated with abdominal surgery and the process of post-operativecleansing of the abdominal cavity. Neumann et al. teaches a somewhatcomplex solution to establishing a re-enterable wound closure, namely, aflexible fabric or plate like securing device that covers the wound,provides a suction tube, and extends outward into a larger, sealabletube that may be re-entered as needed before final closure.

Many other techniques for post-operative temporary wall closure afterabdominal surgery have been described. Studying these techniques enablesthe establishment for objective criteria by which to judge thesuitability of various proposed temporary closure modalities.

A suitable temporary closure should be simple, easy to apply, effectivein containing the abdominal contents, minimally interfere with theabdominal organs and surrounding tissue, minimally, if at all, promotethe formation of adhesions and fistula, and promote process towardsdefinitive closure.

A problem common to many existing methods of temporary wound closure isadhesion formation between the tissue and the material in contact withthe wound. Such adhesions are undesirable, and complicate the process ofpreparing the wound site for final closure. Placing porous materialssuch as gauze, surgical towels and even open cell foam, in directcontact with the open wound site, further complicates final closure byproviding increased surface area that promotes adhesion formation,thereby making removal of this material even more difficult.

Maintaining negative pressure on a wound site without creatingconditions that make the removal of the temporary wound coveringmaterial more difficult, is manifestly beneficial. A desirable layeredwound covering permits both the application of negative pressure and theresultant removal of exuded fluids. Such a covering is re-enterable forthe purpose of cleansing the wound without trauma to the wound site.Such a wound covering would be most advantageous for open abdomensurgical wounds. These devices and techniques could also be used onother types of open wounds that present a difficult healing process.

The need for a wound covering, and therapeutic treatment system thatallows the application of therapeutic negative pressure without causingincreased adverse side effects to the open wound site is apparent.Presently, no such wound covering, or treatment system is known toexist. It is towards the filling of this need that the present inventionis directed.

SUMMARY

An object of the present invention is to provide a layered wounddressing that serves as a temporary covering for an open wound andpermits the application of negative pressure for the removal of exudedfluids from the wound.

A further object of the present invention to provide a wound dressingthat permits the application of negative pressure for the removal offluids from the wound site in a manner that facilitates the healing ofthe wound, and minimizes adhesion formation between the wound dressingand the underlying tissue.

Another object of the present invention to provide a wound dressing thatpermits the application of negative pressure for the removal of fluidsfrom the wound site in a manner that does not promote the formation ofadhesions between the wound dressing and the underlying tissue and yetprovides a porous medium through which the exuded fluids may passwithout experiencing excessive blockage that would degrade theeffectiveness of the negative pressure.

A still further object of the present invention to provide an abdominalwound dressing that serves as a temporary covering for an open abdominalwound and permits the application of negative pressure for the removalof exuded fluids from the wound while being easily retracted from thewound site for the purpose of permitting repeated access to theabdominal cavity for cleansing and/or treatment.

In fulfilment of these and other objectives the present inventionprovides an abdominal wound dressing and methods for its use that permitthe application of negative pressure to the wound site in a manner thatpromotes the healing of the site while limiting the formation ofadhesions that would prevent the removal of the dressing.

According to one aspect of the present invention there is provided aremovable wound closure which comprises a porous pad which is permeableto liquids for placement on or in a wound, the porous pad comprising apolymer foam having interconnecting cells and a sheet of flexibleplastics film having a plurality of holes in its surface, the plasticsfilm being in contact with a surface of the porous pad so that in use,the plastics film is disposed between the surface of the wound and thepad, a film drape which is impermeable to liquids for placement over theporous pad, the film drape having an adhesive perimeter for sealing toan area of skin surrounding the wound and connection means extendingthrough the film drape and in flow communication with the porous pad forconnection to a source of negative pressure for stimulating a flow ofexuded liquids from the wound.

The holes in the flexible plastics film should constitute a sufficientlysmall proportion of the area of the film in contact with the wound sothat there is limited ingrowth of fibrous tissue into the sheet. In thisway, the film does not become adhered to the wound but remainsrelatively easy to remove. Preferably, the holes in the film shouldconstitute less than 10%, especially less than 5% or even 1 to 2% orless of the effective area of the film. Openings in the form of slits orslots are preferred because these constitute a very small proportion ofthe area of the film.

The slits or slots may typically be 0.5 to 2 cms, e.g. 1 to 1.5 cm inlength and may be aligned in rows and separated by 10 to 40 mil spaces,e.g. 20 to 30 mil spaces.

The flexible film should be sufficiently stiff to hold its shape. Asuitable material is plasticised pvc of 30 to 80 microns in thickness,e.g. 40 to 60 microns.

In use, the film is trimmed to size such that it overlaps the woundedge. An absorbent polymer foam, e.g. a reticulated polyurethane foam,is trimmed to size so that it fits within the boundary of the wound. Thetrimmed foam pad is placed on the cut film so that the edges of the filmextend beyond the perimeter of the foam, e.g. by abaout 20 to 80 mm,preferably 40 to 60 mm, typically about 50 mm. A surgical drape ofelastomeric film-like material is placed over the foam pad and theflexible plastics film so as to encapsulate and provide an air-tightseal over the wound dressing. A suction tube or connector is arranged toextend through the surgical drape into the polymer foam or into closeproximity with it. The suction tube or connector is sealed to thesurgical drape so that the space beneath the drape can be maintained ata pressure below atmospheric by connecting the suction tube or connectorto a source of negative pressure. A preferred suction tube connectorhead is described in GB Patent No. 2329127 and in U.S. Pat. No.6,216,701, the disclosure of which is specifically incorporated hereinby reference.

Surgical drapes conventionally comprise a thin elastomeric film which iscoated overall on one side with a tacky, pressure-sensitive adhesive.Usually, a protective sheet which is treated with a release agentcontacts the adhesive surface and is stripped away just before use toreveal the adhesive surface. For the purposes of this invention, theassembly of the adhesive elastomeric film and protective film are cut tosize (and if appropriate, a hole cut for the suction tube or connector)prior to stripping away the protective sheet.

Suitable elastomeric films include polyurethane and polybutadiene.Commerically available surgical drapes include those marketed by the 3MCompany under the trade mark “Tegaderm”.

The foam may comprise multiple layers. A suction tube spigot orconnector is provided on the upper surface of foam for connection to anegative pressure source. Instead of employing a flexible plastics sheetin contact with the wound and a separate portion of polymer foam, thefoam may be enclosed in an envelope of plastics film. In thisembodiment, the plastics film may be elastomeric in nature and the filmneed not extend beyond the perimeter of the foam. However, it isconvenient to provide a flange of film extending beyond the perimeter ofthe foam, e.g. by about 20 to 80 mm, more usually about 40 to 60 mm,typically about 50 mm. Suitable elastomeric film materials includepolyurethane (PTFE), or polybutadiene films, similar to those used forsurgical drapes. Preferably, the elastomeric film has a thickness ofabout 30 to 70 microns, especially 40 to 60 microns, typically about 50microns. A number of differently sized polymer foam slabs will be cut,shaped and enclosed in an envelope of elastomeric film material. It maybe convenient to weld the film to form the envelope using ultrasonic orheat welding. Commonly, abdominal wounds are approximately elliptical inshape and the foam pad is also preferably elliptical in shape. Typicalsizes for the foam pads may be about 280, 320 and 380 mm for the majordimension and about 140, 175 and 250 mm for the minor dimension. Apolyurethane foam having a thickness of about 5 to 10 mm, e.g. about 6mm, is suitable. Polyurethane foams having a pore size of about 30 to50, e.g. 40 pores per inch are preferred. Polyether foams or polyvinylalcohol foams may alternatively be used. If multiple layers of foam areemployed, different foams may be used in different layers. For example,the layer in contact with the lower film may be of polyvinyl alcoholfoam and the upper foam layer(s) may be of polyurethane.

In the multi-layer embodiment, at least one lower layer of foam may beenclosed in elastomeric material and placed in direct contact with thetissue within the open wound. In another embodiment, only a single layerof foam is used, and the envelope of elastomeric material containing thelayer of foam is placed in direct contact with the open wound.

Fluids are drawn by negative pressure through the holes in the flexibleor elastomeric material, and then through the foam. In the multi layerembodiment, fluids are drawn by negative pressure through the holeslocated in the elastomeric envelope, through the lower layer(s) of foam,again through holes in the elastomeric envelope, and then through theupper layer of foam that is placed over the enveloped lower layer(s).

In the multi layer embodiment, the lower layer(s) of foam may be of afiner porosity while the upper layer of foam may be coarser. In allembodiments of the present invention, an adhesive elastomeric sheet,e.g. a surgical drape, covers the entire wound dressing and seals theedges to the skin surrounding the wound. An appropriate vacuum device isattached to the suction tube spigot or connector to provide therapeuticnegative pressure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view of the device of a first embodiment ofthe present invention showing the use of a combination single foam layerwithin an envelope and an overlay of a second foam layer.

FIG. 2 is a cross sectional view of a second embodiment of the presentinvention similar to FIG. 1 but showing the use of a double foam layerwithin an envelope.

FIG. 3 is a third embodiment comprising a flexible sheet and a layer offoam thereon.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

The present invention lends itself to use in conjunction with surgicaltechniques that require repeated access to the abdominal cavity aftersurgery therein. The present invention is directed toward providing aremovable and beneficial dressing that facilitates both healing of thewound and its final closure.

Reference is made to U.S. patent application Ser. No. 08/951,832 andalso to U.S. Ser. No. 09/078,223 and GB Patent No. 2307180 (WO 94/20041and WO 97/18007), for a description of a negative pressure systemsuitable for implementing the vacuum required for use of the dressingstructures, and treatment method, described herein. The disclosure ofthese documents is incorporated herein by reference. Negative pressureis defined herein as a vacuum of less than 1 atmosphere of pressure.Controlling the negative pressure and collecting and disposing of exudedfluids are also described in the above cited references. The manner ofusing such systems in conjunction with the dressing structure describedherein will become apparent to those of ordinary skill in the art.

Reference is made to FIG. 1 for a description of a first embodiment ofthe present invention wherein a single lower layer of foam is utilizedin the wound contact layer of the dressing. Both FIG. 1 and FIG. 2 arepartially exploded views of the dressing of the present invention.During use, the layers of foam and the intervening sheets of elastomericmaterial would be in close and sometimes sealed contact with each other.

The complete wound dressing 10 shown in FIG. 1 comprises upper foamlayer 12 and lower foam layer 36. Lower foam layer 36 is envelopedwithin two sheets of elastomeric material 38 such as are used for themembranes of surgical drapes. The elastomeric sheets 38 may preferablybe constructed from polyurethane film, which provides both the necessarystrength and resiliency needed for placement in direct contact with thewound. Another suitable material is polytetrafluoroethylene (PTFE).Elastomeric sheets 38 are sealed on their periphery, e.g. by welding oradhesive, in a manner that surrounds the lower layer of foam 36.Elastomeric sheets 38 resist the formation of wound adhesions and aretherefore appropriate for placement in direct contact with the tissuesurfaces within the wound and around the wound periphery.

Placing such non-porous film material in contact with the wound opening,rather than open cell foam or a mesh material greatly reduces theoccurrence of adhesions that, over time would make removal of thedressing difficult or dangerous. The pliable and flexible lower layerenvelope is easily inserted over and/or into the wound. The lower layerenvelope may, as desired, be placed either over the wound wherein theedges of the layer are in contact with the skin surrounding the wound orpreferably into the wound leaving the upper surface of the upper surfaceof the lower layer envelope exposed above the wound.

The overall dressing 10 has a generally flat profile as shown in crosssection in FIG. 2 and FIG. 3. The shape of the dressing can varysignificantly depending on the size and shape of the wound to which itis to be applied. A rectangular or square shape having dimensions on theorder of 8 inches by 8 inches up to as much as 18 inches by 18 inchesmight be appropriate for use in conjunction with the abdominal woundsdescribed above. Other dimensions and shapes, such as circular, oval oreven oblong may be suitable for other types of wounds. Typicaldimensions for thicknesses and for planar dimensions of oval orelliptical foam slabs are given above. This basic structure may beeasily implemented with any of these, or even other, shapes and sizes.

Elastomeric sheets 38 are provided with a plurality of holes 32 and 34in the upper and lower walls 28 and 30 of the envelope they define.These holes may be of the order of 3 mm (⅛ inch) to 6 mm (¼ inch) inlength, diameter or maximum dimension and may be dispersed across thesurface of the defined envelope on 25 to 75 mm (1 inch to 3 inch)centres. Preferably, the holes are slit- or slot-shaped. The positionsof the holes may be associated with holes positioned into and throughlower foam layer 36 as described in more detail below. Where holes areprovided in the foam, they may be of different sizes and shapes.

Lower foam layer 36 is preferably constructed from polyurethane having ahigh degree of reticulation and good permeability under suction. Foamshaving at least 90% and preferably 95% of interconnecting cells arepreferred. Preferably, the foams have from 20 to 60 pores per inch.Preferably, the polyurethane foams are prepared by reacting ahydrophilic polyether polyol with a tolylene diisocyanate in thepresence of water. Carbon dioxide is liberated in the reaction whichprovides a gaseous blowing agent. Pore size can be controlled bytemperature and stirring. Reticulation is enhanced by maintaining thefoam in the chamber in which the foam is initially formed and causingthe blowing agent to expand further and rupturing cell walls.

As indicated above, lower foam layer 36 is punctuated by a plurality ofholes that pass entirely though the layer from its upper to lowersurface. As will be seen from their placement with respect to holes 32and 34 in the elastomeric envelope, the holes in the lower foam layer 36are provided to form “sinks” into which the exuded fluids from the woundmay be drawn. Holes 34 in the lower surface of the elastomeric envelope38 may be positioned directly over the holes in the foam layer 36.

Holes 32 in the upper wall 28 of the elastomeric envelope 38 arepreferably positioned so that they are not aligned with the holes in thefoam layer 36 and the holes in the lower wall 30 of the envelope 38. Inthis manner, fluids are withdrawn (by appropriate negative pressure)from the wound into the holes 34 positioned in the lower wall 30 of theenvelope 38 and into the “sink” holes in the lower foam layer 36. Thefluids are then drawn into the cells of the lower foam layer 36 wherethey are dispersed before again being drawn through holes in theelastomeric envelope 38, this time in the upper wall 28 of the envelope38. Placement of the lower foam layer/envelope onto or into the woundtherefore requires proper orientation of the holes as shown.

A problem encountered in the prior art has been the deterioration offlow caused by the clogging of the medium through which the exudedfluids, and the accompanying debris, must flow. Such flows are drawntowards the source of the negative pressure thus becoming clogged mostquickly along the direct path towards the vacuum source, in this casethe suction tube. The present invention disperses the vacuum so as tode-localize the flow. The layers of foam and the spaced holes in theelastomeric sheets provide this dispersion. Even without an interleavedlayer of foam, the off set holes accomplish this purpose. The darkarrows in both FIG. 1 and FIG. 2 show the flow of exuded fluid throughthe dressing.

Upper foam layer 12 provides the initial mechanism for dispersing thevacuum that draws the fluids up from the wound. In the presentlypreferred embodiment as shown in FIG. 1, upper foam layer 12 is acoarser polyester-based or polyurethane foam having greater rigiditythan the lower layer of polyurethane foam. For example, the lower layerof foam 36 may have about 1.5 to 2 times the pores per inch of thecoarser foam layer. Typically, the coarse layer of foam may have 20 to30 pores per inch. Upper foam layer 12 should be somewhat less pliableso as to hold its shape under the influence of even relatively strongnegative pressure. Upper foam layer 12 is placed in direct contact withthe upper wall 28 of the elastomeric envelope 38 containing lower foamlayer 36. Covering upper foam layer 12 and the balance of the dressingis elastomeric drape 14, which in the preferred embodiment is made ofthe same type of polyurethane film, as is elastomeric envelope 38.

Drape 14 is a single sheet, cut large enough to fully cover upper foamlayer 12 and an additional area of skin surrounding the wound site. Apressure sensitive adhesive, such as a permanently tacky acrylicadhesive, is coated on at least the periphery of drape 14 for creatingan airtight seal against the skin, effectively closing the dressing andthe wound beneath it.

Connector 16 is positioned over a hole 24 cut in drape 14 and is fixedthereto by sealing patch 22. Sealing patch 22, which is circular in thepreferred embodiment, adheres to a bottom flange portion 20 of connector16 as well as drape 14. In this manner, a negative pressure is drawn inupper foam layer 12 when an appropriate suction line is attached to tubeconnector 18 positioned on connector 16. Flange portion 20 may have alower surface shaped with channels to direct flow of fluid from theporous pad to the tubular portion 18 of the connector. A suitablesuction head connector is shown in GB 2329127 and in U.S. Pat. No.6,216,701 (WO 99/13793).

Another embodiment of the present invention is depicted in FIG. 3. Inthis embodiment, the principles of operation are identical, but thedressing is comprised of but a single foam layer, the foam layer withinthe non-porous film is dispensed with. The foam utilized is blackcoloured open cell polyurethane currently commercialised in assignee'sV.A.C. product.

Referring to FIG. 3, a flexible sheet 38 of semi-stiff plasticsmaterial, e.g. formed from plasticized pvc is placed in contact with thewound so that the trimmed edges line the walls of the wound. The sheetis formed with holes 34 which are preferably slits or narrow slots. Areticulated plastics foam is placed on top of the sheet 38. A suctionhead connector 16 is placed with its flange portion 20 in contact withthe top surface of the foam pad and a surgical drape 14 is placed overthe foam and the sheet 38 to seal the dressing in the wound.

Instead of providing a separate sealing patch 22 to seal the connectorto the dressing, the patch may be part of the surgical drape, asdescribed and illustrated in GB 2,329,127 and U.S. Pat. No. 6,216,701.

The dressing structure of the present invention could be applied in anumber of circumstances in association with a variety of different woundtypes. In the case of an open abdominal wound as might result fromsurgery, the lower foam layer contained within the elastomeric envelopewould be positioned within the wound with the periphery possiblyextending under the fascia and peritoneum of the abdominal wall. Theupper foam layer could then be cut to a size appropriate for positioningon the exposed upper surface of the lower layer envelope. The drape withthe appropriately positioned spigot may then be placed over the upperfoam layer and the wound as a whole, extending two or more inches overthe skin surrounding the wound, and adhesively holding the dressing inplace. Application of a suction line as described above draws the entiredressing onto the wound and serves to initiate the flow of effluentthrough the dressing.

The thickness of the upper and lower foam layers is determined in partby the desire to have a flat profile to the dressing when it is inplace. The more rigid upper layer of foam may, in the preferredembodiment, have a thickness on the order of 25 to 75 mm (1 inch to −3inches) uncompressed. Its rigidity should limit compression to 80%-90%under the negative pressures normally associated with wound suction andthe like. The more pliable lower foam layer, where employed, should havea thickness on the order of 5 to 15 mm, e.g. 5 to 10 mm (about ¼ to ¾inch) so as to be capable of being easily inserted into the wound.

The structure of the present invention may likewise be utilized on thesurface of the skin when the open wound is not associated with aninternal cavity or the like. In such a case the periphery of theelastomeric lower envelope may contact the skin surrounding the wound.This is appropriate as long as the periphery of the drape covering theupper foam layer extends suitably beyond the lower envelope to adhere tothe skin and seal the dressing. It therefore becomes apparent that thelower elastomeric envelope may be pre-made in a variety of shapes andsizes while the upper foam layer and the drape may be cut, at the timethe dressing is placed on the wound, to the appropriate size andconfiguration.

FIG. 2 discloses an alternate preferred embodiment of the presentinvention wherein the single lower layer of foam shown in FIG. 1 isreplaced with a double layer of foam. In this embodiment, elastomericenvelope 38 encloses a first lower foam layer 40 and a second lower foamlayer 42. The advantage realized by this arrangement lies in the offsetpositioning of the holes interspersed in both foam layers. Holes 34punctuating the lower wall 30 of elastomeric envelope 38 remainpositioned in line with the “sink” holes positioned in the second(bottom) layer of foam 42. Holes 32 punctuating the upper wall 28 ofelastomeric envelope 38 are, as described above, offset from alignmentwith holes 34 in the lower surface of the envelope, but are aligned withthe “sink” holes positioned in the first (top) layer of foam 40. Underthis structure further dispersion of the flow of fluid occurs thusdecreasing the localization of clogging debris and prolonging theeffective life of the dressing. The remaining components, applications,and methods of use of the dressing are as described above in conjunctionwith FIG. 1.

The present invention has been described in conjunction with certainpreferred embodiments. Alternative embodiments and further applicationsof the invention will be anticipated by those skilled in the art withoutdeparture from the basic concepts and principles of the invention.Certain materials have been described as suitable for the specificlayers of foam and film although a variety of similar materials would beequally suitable. Certain geometries and dimensions have been describedas appropriate under various conditions and with various applications ofthe dressing, especially in conjunction with open and re-enterableabdominal wounds. These geometries and dimensions are not intended aslimiting but are described as representative of the various shapes andsizes possible using the fundamental layered structure of the dressing.The scope of the invention is therefore not limited by the foregoingdescription but is best defined by the specific claims that follow.

1.-16. (canceled)
 17. A method for treating a patient, said method comprising: positioning an envelope member having a plurality of holes formed on the envelope member within a cavity of the patient, the envelope member having a foam material having a plurality of transverse holes encompassed within an interior space of the envelope member; sealing the envelope member within the cavity with a drape positioned in contact with an area of skin surrounding the cavity; and providing a negative pressure to a sealed space beneath the drape for drawing fluids from the cavity.
 18. (canceled)
 19. The method according to claim 17, further comprising sizing the drape to be capable of contacting the area of skin surrounding the cavity prior to positioning the drape in contact with the area of skin surrounding the cavity.
 20. (canceled)
 21. A dressing for removing fluid from a wound when subjected to a negative pressure, the dressing comprising: an envelope member enclosing an interior space and having a wound-facing side comprising an adhesion-resistant film for contacting the wound and a second side for receiving a negative pressure, both the patient-facing side and the second side including a plurality of holes; a foam material disposed within the interior space of the envelope member and including a plurality of transverse holes; and wherein the holes in the patient-facing side and the second side and the transverse holes provide a path for removing fluids absorbed from a wound through the foam material.
 22. The dressing of claim 21, wherein the holes in the second side are offset from the holes in the patient-facing side.
 23. The dressing of claim 21, wherein the holes in the second side are aligned with the holes in the patient-facing side.
 24. The dressing of claim 21, further comprising a porous pad disposed over the second side.
 25. The dressing of claim 21, wherein the plurality of transverse holes are aligned with the holes in the patient-facing side.
 26. The dressing of claim 21, wherein the plurality of transverse holes are aligned with the holes in the patient-facing side and are offset from the holes in the second side.
 27. The dressing of claim 21, wherein the plurality of transverse holes are offset from the holes in the patient-facing side.
 28. The dressing of claim 21, wherein the plurality of transverse holes are offset from the holes in the patient-facing side and are aligned with the holes in the second side.
 29. The dressing of claim 21, wherein the foam material comprises a first foam layer and a second foam layer, wherein the first foam layer has a first plurality of transverse holes and the second foam layer has a second plurality of transverse holes, and wherein the first plurality of transverse holes are aligned with the second plurality of transverse holes.
 30. The dressing of claim 21, wherein the foam material comprises a first foam layer and a second foam layer, wherein the first foam layer has a first plurality of transverse holes and the second foam layer has a second plurality of transverse holes, and wherein the first plurality of transverse holes are offset from the second plurality of transverse holes.
 31. The dressing of claim 21, further comprising a suction line fluidly coupled to the tubular portion.
 32. The dressing of claim 21, wherein the foam material has a rectangular cross section.
 33. The dressing of claim 21, wherein the foam material includes a plurality of cells.
 34. The dressing of claim 21, wherein the foam material includes a plurality of cells, and further comprising a source of negative pressure in flow communication with the suction line.
 35. The dressing of claim 21, wherein the plurality of holes is a plurality of slits.
 36. The dressing of claim 21, wherein the envelope member comprises polyurethane.
 37. The dressing of claim 21, further comprising a drape disposed over the second side.
 38. The dressing of claim 21, further comprising a drape disposed over the second side; and a tube connector positioned through the drape.
 39. The dressing of claim 21, further comprising a drape disposed over the second side; and a porous pad disposed between the drape and the second side.
 40. The dressing of claim 21, further comprising a drape disposed over the second side; a porous pad disposed between the drape and the second side; and wherein the porous pad is more rigid than the foam material. 